feature: add update function for safe feature update

Disallow update of any features that are defined by LND (since
just updating the feature, but not the functionality will result in
strange behavior). All known feature bits should be toggled using
protocol config options.

feature/manager_internal_test.go

@@ -135,3 +135,113 @@ func testManager(t *testing.T, test managerTest) {
 		assertSet(lnwire.StaticRemoteKeyOptional)
 	}
 }
+
+// TestUpdateFeatureSets tests validation of the update of various features in
+// each of our sets, asserting that the feature set is not partially modified
+// if one set in incorrectly specified.
+func TestUpdateFeatureSets(t *testing.T) {
+	t.Parallel()
+
+	// Use a reduced set description to make reasoning about our sets
+	// easier.
+	setDesc := setDesc{
+		lnwire.DataLossProtectRequired: {
+			SetInit:    {}, // I
+			SetNodeAnn: {}, // N
+		},
+		lnwire.GossipQueriesOptional: {
+			SetNodeAnn: {}, // N
+		},
+	}
+
+	testCases := []struct {
+		name     string
+		features map[Set]*lnwire.RawFeatureVector
+		err      error
+	}{
+		{
+			name: "unknown set",
+			features: map[Set]*lnwire.RawFeatureVector{
+				setSentinel + 1: lnwire.NewRawFeatureVector(),
+			},
+			err: ErrUnknownSet,
+		},
+		{
+			name: "invalid pairwise feature",
+			features: map[Set]*lnwire.RawFeatureVector{
+				SetNodeAnn: lnwire.NewRawFeatureVector(
+					lnwire.FeatureBit(1000),
+					lnwire.FeatureBit(1001),
+				),
+			},
+			err: lnwire.ErrFeaturePairExists,
+		},
+		{
+			name: "error in one set",
+			features: map[Set]*lnwire.RawFeatureVector{
+				SetNodeAnn: lnwire.NewRawFeatureVector(
+					lnwire.FeatureBit(1000),
+					lnwire.FeatureBit(1001),
+				),
+				SetInit: lnwire.NewRawFeatureVector(
+					lnwire.DataLossProtectRequired,
+				),
+			},
+			err: lnwire.ErrFeaturePairExists,
+		},
+		{
+			name: "update existing sets ok",
+			features: map[Set]*lnwire.RawFeatureVector{
+				SetInit: lnwire.NewRawFeatureVector(
+					lnwire.DataLossProtectRequired,
+					lnwire.FeatureBit(1001),
+				),
+				SetNodeAnn: lnwire.NewRawFeatureVector(
+					lnwire.DataLossProtectRequired,
+					lnwire.GossipQueriesOptional,
+					lnwire.FeatureBit(1000),
+				),
+			},
+		},
+		{
+			name: "update new, valid set ok",
+			features: map[Set]*lnwire.RawFeatureVector{
+				SetInvoice: lnwire.NewRawFeatureVector(
+					lnwire.FeatureBit(1001),
+				),
+			},
+		},
+	}
+
+	for _, testCase := range testCases {
+		testCase := testCase
+		t.Run(testCase.name, func(t *testing.T) {
+			t.Parallel()
+
+			featureMgr, err := newManager(Config{}, setDesc)
+			require.NoError(t, err)
+
+			err = featureMgr.UpdateFeatureSets(testCase.features)
+			require.ErrorIs(t, err, testCase.err)
+
+			// Compare the feature manager's sets to the updated
+			// set if no error was hit, otherwise assert that it
+			// is unchanged.
+			expected := testCase.features
+			actual := featureMgr
+			if err != nil {
+				originalMgr, err := newManager(
+					Config{}, setDesc,
+				)
+				require.NoError(t, err)
+				expected = originalMgr.fsets
+			}
+
+			for set, expectedFeatures := range expected {
+				actualSet := actual.GetRaw(set)
+				require.True(t,
+					actualSet.Equals(expectedFeatures))
+			}
+		})
+	}
+}